Many medium speed diesel engines have a cylinder assembly often referred to by mechanics and the manufacturers as a “power assembly”. The power assembly often consists of several subcomponents which are typically replaced as a unit on the engine to expedite repairs and to assure the integrity of the assembled replacement parts. In the case of the General Electric Evolution Series engine, the power assembly consists of a cylinder head (complete with intake and exhaust valves), a cylinder liner, a piston with compression rings, a crankshaft connecting rod attached to the piston and a “strongback”. The strongback is a casting which the cylinder head attaches to with bolts. The strongback holds the cylinder liner by way of an interference fit between its bore and the outside diameter of the cylinder liner. Also, the strongback holds the high pressure fuel pump, intake and exhaust cam followers. The strongback assembly, including the head in turn is secured to the engine block with four large hold down studs. A fuel injection nozzle is mounted in the cylinder head. The piston with its rings assumes a reciprocating motion based on the rotational movement of the crankshaft's eccentric lobes or throws. The piston rings and cylinder liner are primary wear parts and require periodic replacement, most often at a prescribed interval characterized as an engine overhaul.
Water circulates between the outside of the cylinder jacket and the inside bore of the strongback in a cavity to remove the heat of combustion so as to promote engine bearing life and overall performance. There are two O-rings placed in grooves on the outside diameter of the cylinder liner that contain the cooling water and isolate the water so as to prevent contamination with the lubricating oil in the crankcase below.
Unfortunately, these O-rings are inclined to fail prematurely, resulting in significant water leaks. Due to the absence of any low water detection device, the Evolution engine can operate with little or no cooling water. This can result in cracks on the firing face of the cylinder head and exhaust valve seats, creating additional water leaks. These water leaks are not readily detectable because the heat of combustion creates steam which in turn is conducted out the exhaust valves to the exhaust manifold and turbocharger.
One current method of dealing with this significant problem of cylinder O-ring failures is a procedure in which the cylinder heads are removed from the strongback while the engine remained in the locomotive carbody. The cylinder liner is then forced out of the bore of the strongback using the rotation of the crankshaft as the piston comes up against a fixture placed in the liner bore. This allows replacement of the failed O-rings on the lower, outside diameter of the cylinder liner, after which, the liner is forced back into position within the strongback using power wrenches to drive threaded nuts downward on the four hold-down studs.
This method has two serious drawbacks. First, it offers no opportunity to assess if the cylinder head is leaking, another potentially prevalent source of internal water leaks. Secondly, aside from being an awkward, labor intensive process, the method is disadvantageous because of its unfortunate tendency to damage the newly applied liner O-rings as the cylinder liner re-entered the bore of the strongback. This often results in an unacceptable success rate for the repair process.
The disclosed system and methods of testing and disassembling the power assembly is directed to overcoming one or more of the problems listed above.